Threshold-based sync-mark detection is a commonly used scheme in read channel systems. Detection is performed based on a Euclidean distance between a read-back signal and target sync-mark values. A threshold is set for sync-mark detection based on an anticipated distinction between a sync-mark and a preamble. Performance of sync-mark detection is determined by the sync-mark pattern and threshold, and is calculated based on analytical models or synthetic waveforms. It is important for the performance of a system to find a good sync-mark pattern and threshold for a particular read channel. However, theoretically optimal sync-mark patterns and thresholds may not correspond to real hard drives.
Consequently, it would be advantageous if an apparatus existed that is suitable for dynamically adjusting the sync-mark threshold base on real data.